Fiber optic connector with compensating mechanism

ABSTRACT

A fiber optic connector includes a connector assembly for connecting a fiber optic cable thereto. The connector assembly includes an arrangement whereby the cable can be crimped and attached to the connector without crimping force being exerted on the buffer layer of the cable. The connecting end of the connector has the capillary ferrule extending outwardly therefrom in a spring loaded manner. In connection with another connector the respective ferrules are held in a centering sleeve and retract against the compressive force of a spring into each connector thereof to ensure alignment and tight connection between the core elements held by the ferrules. In order to permit repeat connections, the ferrules are held non-rotatably within the connectors. Further compensating means is provided for ensuring that the fiber core of the cable is maintained flush with the end of the capillary ferrule at all times and under varying temperature conditions.

BACKGROUND OF THE INVENTION

This invention relates to an optical fiber mechanism and connectorassembly employing same for performing connection with precisepositioning of fiber optic cables and the core optical fiber thereof.More specifically, this invention relates to such a connector for usewith both single and multimode fibers, but the preferred embodimentfinds special use with single mode fiber optic cables.

The use of optical fibers as a means for transmitting optical signals inthe field of optical communications has been known for many years. Whenemployed in such systems, it is necessary to interconnect different corefibers within the system to complete the communications link. However,in such connections it is often found that not only are theretransmission losses when the light is transmitted through the opticalfibers, but extensive transmission losses also result from the actualfiber interconnections themselves.

In order to eliminate or minimize such interconnection losses, fiberalignment must be achieved with accuracy on the order of microns, and atthe same time the fibers have to closely abut in a manner such as to notdamage the cleaved or cut fiber ends. More particularly, in the pirorart in connecting the fiber ends, a grinding or rotating movement oftenoccurs and the ends of the fibers become damaged or scarred thereby,resulting in additional transmission losses. Moreover, although thefiber ends will initially be in abutment upon initial connection, due totemperature changes, the fibers expand or contract ultimately resultingin a gap between fiber ends and consequently, additional interferencelosses.

One prior art approach to centering the fibers or waveguides withinaligned connections is disclosed in U.S. Pat. No. 4,440,469 toShoemaker. The device of Shoemaker is an SMA-style optical waveguideconnector, the type to which this invention is directed, and includes atubular contact body having an axial passageway profiled for receiving aprimary ferrule therein. The passageway is further profiled forretaining the primary ferrule at a rearward location, which ferrulereceives an optical waveguide therethrough with a forward end segment ofthe waveguide extending forward from a forward end of the contact body.An alignment ferrule is provided and is mounted over the forward end ofthe contact body and received on a forward segment of the opticalwaveguide. The forward end of the primary ferrule and the inner profileof the contact body passageway are structured to interfit and define aregion wherein adhesive material is inserted from the forward terminalend of the connector assembly. The adhesive is retained within thisregion by the alignment ferrule which fits over the forward segment ofthe optical waveguide.

Although initially aligning the fiber very precisely, as the adhesivesets, some shrinkage of the adhesive occurs in the device of Shoemaker,and it is not possible to achieve fine fiber alignment readily andreliably with such an arrangement. Moreover, the use of the adhesivecomplicates the assembly operation and requires long setting times andoften, due to the setting of the adhesive, as noted above, even ifmisalignment does not occur, changes in temperature will cause shrinkageor expansion of the adhesive ultimately resulting in creation of a gapand in the fiber ends being moved out of abutment with each other.

An alternative approach to solving these problems is disclosed in U.S.Pat. No. 4,487,474 which teaches the use of a pair of ceramic opticalplugs having optical fibers extending coaxially therethrough which fitwithin a ceramic sleeve. A coupling nut is used to hold the two plugstogether to effect the interconnection between the optical fibers.

Although generally providing improved results over the adhesiveemploying prior art systems, the connector employing the ceramic plug asdisclosed in this patent includes disadvantages in that it is difficultto ensure that the two ceramic plugs are tightly held against eachother, and further, there is the possibility of rotation of the plugsand fibers with respect to each other will result in scarring of thefiber faces upon repeated connection and disassembly of the connectordevice. As previously noted, such scarring can cause significanttransmission losses at the interface. Further, as noted previously,although it is possible to maintain the plugs in abutment, it is oftenthe case that the fibers will shrink into the plug due to temperaturechanges, which results in an interference causing gap between the fiberends.

In another known prior art device the plugs are used with adhesive toensure that the fiber ends remain flush with the plugs. However, thistype of system requires polishing and buffing of the ends of the fibers.This buffing will often result in the end faces becoming concave in thedirection of its respective holding plug. Thus, in assembling the twoplugs against each other a gap will result between the concave endsurfaces will all the attendant disadvantages discussed above.

The above-discussed gaps between fiber ends while causing interferenceare not as disruptive in the case when multimode fiber optic cables areused. However, in the case of single mode fiber optic cables, theresultant gap can cause unacceptable transmission losses. In the priorart there are only several ways to reduce these losses in the case ofsingle mode fiber optic cables.

One solution provided is to epoxy the fibers in place, but this includesall the disadvantages discussed above. A second approach is to use anarrangement of several ferrules concentrically assembled in what isknown as a "stratus" configuration. However, this arrangement is stillprone to gap creation and is generally not satisfactory. Moreover, thisarrangement is also very complicated to assemble. A third arrangement,which is more satisfactory in terms of results, is a technique ofmolding the fiber into a molded connector.

Such molded connectors or methods of molding connectors are disclosed inU.S. Pat. Nos. 4,107,242; 4,213,932; 4,264,128; and 4,512,630. Althoughproviding improved results, these devices are complicated to assemblerequiring complicated molding devices. As a result expenses areincreased. Moreover, the devices are not field terminable.

As can be seen, the prior art systems suffer from a number ofdisadvantages at the fiber connection ends. Moreover, the connectorsthemselves do not provide a simple and secure method of attaching thefiber optic cables to the connector assembly itself. Generally, sometype of simple crimping arrangement is employed resulting in a danger ofthe internal waveguide or core fiber of the fiber optic cable beingdeformed or damaged as a result of the crimping operation. Moreover,simple crimping is often not satisfactory in terms of holdingefficiency.

SUMMARY OF THE INVENTION

In order to overcome the above-discussed disadvantages discussed withreference to the prior art, the inventio provides an epoxiless andpolishless fiber optic cable connector of simple construction which canbe rapidly and easily assembled and disassembled in the field. Further,the invention provides a fiber optic cable connector having in apreferred embodiment a temperature compensating mechanism to ensure thatthe fiber ends of respective connectors are always in physical contact.In a still further aspect the invention provides an improved mechanismfor connecting a cable to a connector.

As noted above, in one aspect the invention resides in a fiber opticconnector made up of body having means for connecting a fiber opticcable to one end thereof, with the buffered fiber and bare optical fiberof the cable extending into the body of the connector. Fiber retentionmeans is provided for holding a portion of the buffered fiber at aterminated portion thereof with the bare fiber extending from the bufferlayer, in fixedly secured relationship with respect to the fiberretention means, and through the body. A capillary ferrule slidablyreceives the portion of the bare fiber therein and is held by acapillary retainer in fixed relationship with respect thereto, and in amanner extending from the other end of the body such that the capillaryretainer mechanism is retained within the body. A main spring serves tourge the capillary retainer toward the other end of the body forpermitting the capillary ferrule to retract into the body when theconnector is connected to a like connector.

In addition, in single mode applications it is preferred that amechanism cooperates with the above to permit termination of the corefiber in a manner such that it is always maintained flush with the endcapillary ferrule. Thus, when employed to connect to another fiber end,the mechanism functions to effect relative position compensation withrespect to the elements of the connector so that the two fiber ends willbe in physical contact under all conditions. In a more specific aspectthe connector includes a key mechanism for preventing rotation of thefiber core relative to the connector body and for ensuring a keyedposition interconnect with a like connector. The connector furthercomprises, in combination, an adaptor body having centering means forcentering respective capillary ferrules of like connectors and forconnecting two connector bodies to each other.

The compensating mechanism discussed above includes, preferably, atwo-part fiber clamp for clamping the bare fiber. The two parts are heldtogether by a clamp body. The clamp body is spring loaded in a mannersuch as to permit relative movement between the bare fiber and thecapillary ferrule for temperature compensation and to ensure abutmentbetween fiber ends even under misalignment conditions, and with asufficiently low force to prevent breakage of the ends of the fibers andto not disturb transmission between the fiber ends.

In still another aspect the invention relates to the means forconnecting the fiber optic cable to the one end of the body. The meansfor connecting the cable comprises a crimpable structure at the end ofthe body which fits over the outer jacket of the cable. An inner sleeveis received coextensively with the crimpable structure around the bufferlayer holding the jacket and strength member layer between the innersleeve and the crimpable structure. The crimpable structure is crimpedto hold the jacket and strength layer between it and the inner sleeve.To provide more secure holding, the inner sleeve can also be crimpedonto the buffered fiber prior to crimping of the crimpable structure.Although described with reference to a fiber optic cable, this mechanismwill also function effectively on any type of multi-layer cable capableof permitting insertion thereinto of such an inner sleeve as described.

In addition, the device of the invention provides a free floatingstructure which permits a limited amount of movement of the cable fiberin a direction transverse to the longitudinal axis of the connector.This allows compensation between misaligned fiber ends of differentconnectors so that precise alignment between the fiber ends of differentconnectors can be repeatedly and reliably obtained. Further, to enhancesuch performance, the connector also permits movement of the fiber endsalong the longitudinal axis thereof ensure abutment between fiber endsunder all conditions.

Accordingly, it can be seen that the device of the invention providesone advantage in that it facilitates secure connection of a fiber opticcable to a connector without the risk of deformation or damage to theoptical fiber or waveguide of the fiber optic cable. In addition, theconnector provides for secure and tight connectio between two opposedwaveguides in a manner such that little or no damage, due to the lowforces exerted on the fiber ends, is done to the end of the waveguidesdue to repeated connections being effected. Moreover, the connectiobetween the waveguides is done in a manner that results in very lowtransmission losses between the respective two fibers or waveguides ofthe cables. Further, the fiber and cable are only held mechanically. Noepoxy or chemicals are employed. Moreover, it is possible to cleave thefiber after the connector has been almost completely assembled, or evenfully assembled. Thus, the probability of erroneous positioing of thefiber ends with respect to the ferrule, breakage of the fiber ends ordirt accumulation prior to or during assembly.

Other features and attendant advantages of the invention will be morereadily apparent as the same becomes better understood from thefollowing detailed discussion made with reference to the accompanyingdrawings in which like reference numerals designate like partsthroughout the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view, in particular cross-section, of aconnector assembly in accordance with a preferred embodiment inventionshown in assembled condition;

FIG. 1B is a perspective view, in partial cross-section of an adaptorfor use with the connector of the invention;

FIG. 2 is an exploded view, in partial cross-section of the connectorassembly of FIG. 1A;

FIG. 3 is a side cross-sectional view of the connector assembly of FIGS.1A and 2;

FIG. 4 is an exploded view in partial cross-section of the capillaryferrule, capillary retainer, clamp, clamp body, compensating mechanismand key mechanism of the preferred embodiment of the connector accordingto the invention; and

FIGS. 5a and 5b are side views, in cross-section of the operation of theclamp body, capillary retainer and clamp body spring mechanism of theinvention to ensure termination of the fiber flush with the end of theferrule at all times after the connector is assembled;

FIGS. 6 and 7 are perspective views of alternative constructions ofcentering sleeves which can be employed in the adaptor of the connectionof the invention;

FIG. 8 is an exploded view, in partial cross-section of portions of theconnector of the invention showing an alternate embodiment of theclamping mechanism for the fiber optic cable; and

FIG. 9 shows in cross-section an alternative embodiment of the connectorof the invention especially adapted for use with multimode fiber opticcables.

DETAILED DISCUSSION OF THE INVENTION

This invention provides an apparatus for rapidly connecting the ends oftwo opposed fiber optic waveguides or bare fibers of fiber optic cables,and especially in a preferred embodiment for the connection ofrespective fibers of fiber optic cables of the single mode type. Theinvention also has use in the preferred as well as in an alternativeembodiment, in connecting fiber optic cables of the multimode type. Moreparticularly, the invention involves a connector assembly which iscapable of connecting a fiber optic cable effectively and securely toone end of a fiber optic connector and of supporting and holding both aportion of buffered fiber and the bare fiber of the fiber optic cable,without use of epoxy or other adhesive, through the body of theconnector for connection in direct physical contact at all times, notwithstanding temperature effects, with an opposing bare fiber end heldby a like connector.

The connector assembly in accordance with a preferred embodiment of theinvention is generally shown in FIGS. 1A, 1B, 2 and 3 and unlessotherwise noted will be described generally with reference to saidFigures.

As shown in FIGS. 1A, 1B, 2 and 3, in a preferred embodiment theconnector assembly includes a rear body 3 within which is housed themajority of the components of the assembly. The body 3 includes at oneend thereof a crimpable extension 37 extending therefrom for havingcable 27 slid thereinto. The cable 27 is preferably a single mode fiberoptic cable of the type having an outer jacket 29, an intermediate layerof strength fibers 31, typically Kevlar® type fibers commerciallyavailable from Dupont Corporation, a buffered fiber layer 33 and aninner bare fiber 35. However, the invention can also be employed withcables of the type having multiple fibers surrounded by the buffer layer33.

To connect the cable 27 to the rear body 3, the jacket 29 and strengthlayer 31 of the cable is terminated at a predetermined point withrespect to the buffer 33 and bare fiber 35, with the buffer 33 and barefiber 35 each extending a predetermined distance from the discussedtermination point. An inner sleeve 21 is slid over the fiber 35 andbuffer 33 so as to be received within the strength layer 31 andgenerally substantially coextensive with the crimpable extension 37. Tohold the cable 27 to the rear body 3, the extension 37 is crimped ontothe cable 27 to hold the jacket 29 and strength layer 31 between it andthe inner sleeve 21.

In one embodiment the inner sleeve 21 is made of metal and is generallynon-deformable relative to the extension 37. This serves to protectbuffer 33 and fiber 35, and to provide a rigid base onto which to crimp.Alternatively, to provide more secure attachment the inner sleeve 21 canalso be deformable and crimped onto the buffer 33 prior to crimping ofthe extension 37. In this latter case, the sleeve 21 will be slightlylonger, as shown in dashed lines 21a in FIG. 3, and projects out fromthe strength layer 31 to provide a crimping surface.

A boot 23 having engaging means 24 can be used to cover the connection,as shown, and engages with corresponding engaging means 38 of theextension 37. The boot 23 can be typically made of rubber and provides astrain relief function.

Once connected to the rear body 3 a portion of buffered fiber 33 and aportion of bare fiber 35 extend through the rear body 3 toward the otherend thereof. Inside the rear body 3 is received a main spring 19 whichabuts at one end against abutments 4 on the interior of the rear body 3.Also received within the rear body 3 is a spacer ring 8 which serves asan abutment on one side thereof for the other end of the main spring 19.

Prior to assembling the connector, preferably a two part fiber clamp 17,preferably of plastic material, is clamped in part onto the bufferedfiber 33 and partly on the bare fiber core 35 of the cable 27. Thebuffer 37 extends for a predetermined distance into the clamp 17 and isthen terminated. The clamp 17 is a two part clamp having members 17a and17b, each having V-shaped groove portions 17c and 17d different sizes.Further, at the end proximate the spring 19 the clamp 17 includes alarger diameter portion 17e.

To provide the necessary clamping, the corresponding V-shaped portions17d are dimensioned to be, when the clamp 17 is assembled, slightlysmaller than the diameter of the buffered fiber 33 for holding thebuffer at said V-shaped portions 17d. The larger V-shaped portions 17dthen taper into smaller size V-shaped portions 17c which serve to holdthe bare fiber 35 between the two clamping members 17a and 17b. In thiscase, the space provided by V-shaped portions 17c when clamp 17 isassembled is slightly smaller than the diameter of bare fiber 35 so thatthe bare fiber 35 is held firmly thereby. The members 17a and 17b arethen held together by clamp body 11 which is made up typically of ametal sleeve split having a cut-out portion 11b as more clearly shown inFIG. 4, in partial cross-section, which includes keying tabs 11a whosefunction will be described hereinafter. In a preferred embodiment, thelarger diameter portion 17e serves the purpose of preventing the members17a and 17b from being inserted further than a predetermined distanceinto the clamp body 11. This larger diameter portion 17e is notnecessary and can be replaced by other equivalent features orstructures.

Over the clamp body 11 is slidably received a compensator body sleeve 9having a smaller diameter portion 9a and a larger diameter portion 9b.In addition, a clamp body spring 13 is received around the clamp body 11in abutment between the end of smaller diameter portion 9a and keyingtabs 11a. The compensator body sleeve 9 is held on the clamp body 11 byturned out tabs 11b of clamp body 11, as is more clearly shown in FIG.3.

A capillary retainer 7 is slidably received over clamp body 11 and inabutment with the end of smaller diameter portion 9a of compensator body9. Slots 7b are provided in the capillary retainer 7 as clearly shown inFIG. 4 for engaging tabs 11a to maintain the clamp body 11 innon-rotational relationship with respect to the capillary retainer 7 butin slidable relationship along the longitudinal axis with respect toeach other. In this regard, the capillary retainer 7 includes a wall 7chaving a thickness less than the length of tabs 11a as will be explainedhereinafter. The wall 7c includes a passage 7a in the center thereof,typically press-fit engaging a capillary ferrule 25 therein. The ferrule25 is typically a conventionally manufactured ceramic ferrule. Theferrule includes a larger passage portion 25b to permit initial ease ofpassage of the bare fiber 35 thereinto and tapers into a smaller passageportion 25a which permits sliding of the bare fiber 35 with respect tothe ferrule 25, but prevents excessive transverse movement to therebyensure centered optical alignment when connected to a like ferrulehaving a like bare fiber therein.

Prior to assembly of the connector, the rear body 3, spring 19 andspacer 15 are held over the cable 27 with the clamp 17, clamp body 11,compensator body 9 clamp body spring 13, capillary retainer 7 andcapillary ferrule 25 assembly spaced therefrom. The buffer 33 and barefiber 35 are held as described with the bare fiber 35 extendingoutwardly from the capillary ferrule 25. As previously discussed, thetabs 11a are longer than the thickness of wall 7c and extend therefromin the direction of the free end of capillary ferrule 25. In order toterminate the bare fiber 35 in a manner such that the bare fiber 35 willalways be flush with the end of capillary ferrule 25, the clamp body 6is compressed against clamp body spring 13 an amount sufficient that theends of tabs 11a are flush with the face of wall 7c. The bare fiber 35is then cleaved flush with the end face of capillary ferrule 25. Thecleaving sequence is clearly shown in FIGS. 5a and 5b. The method ofcleaving the fiber flush with the mating face is known to those ofordinary skill in the art and can be conducted in accordance with themethod described in U.S. application Ser. No. 474,099 filed Mar. 10,1983 (now U.S. Pat. No. 4,643,520) of one of the herein named inventors,and which disclosure is specifically incorporated by reference herein.Accordingly, the thus cleaved bare fiber 35 will require no polishing orbuffing as is required in the prior art connectors.

Once cleaved, the clamp body spring 13 is allowed to relax and as aresult, the end of the bare fiber 35 will extend partially beyond thefree end of capillary ferrule 25 as shown in FIG. 5B. At this stage, theconnector is ready to be assembled. This relative positioning and changein positioning is more clearly shown in FIGS. 5a and 5b as was discussedabove.

To assemble the connector, the rear body 3 and associated elements arebrought over the clamping ferrule assembly. The crimping extension 37and optionally the inner sleeve 21 are crimped to secure the cable 27 tothe rear body 3. A front body 1 having inner threads 1a is then threadedonto corresponding threads 3a of the rear body 3 with the previouslydiscussed assembly held therein. In this regard, the rear body 3 alsoincludes a key tab 3b which engages with a corresponding slot 50 in thecapillary retainer 7 to prevent rotation of the capillary retainer 7relative to rear body 3. This is more clearly shown in FIGS. 1A, 2 and4. In this regard, the slot 50 must be sufficiently long to permitmovement of the capillary retainer 7 rearwardly so that the connectorand ferrule 25 can be connected to a like connector and ferrule 25through the adaptor 40 as will be discussed hereinafter.

The front body 1 also includes a coupling nut 5 rotatably engaged withrespect thereto to be threadably engaged through threads 5a to theadaptor 40 to be discussed hereinafter. The coupling nut 5 is expandedduring assembly for connection to the front body 1 as shown. Further,the front body 1 also includes a key tab 6 which is integral therewithas a bent-out portion, and which ensures precise connection relative toa fixed rotational position with respect to the adaptor 40 by engagingthe cut-out portion 55 of the adaptor 40 as seen in FIGS. 1B and 3.

Inside the rear body 3, the spacer 15 is received over the largediameter portion 17e of clamp 17 and the end tabs 11b of clamp body 11,and abuts against the large diameter end of compensator body 9. Inassembled condition the tabs 11a abut against wall 1b of front body 1forcing the clamp body 11 back against clamp body spring 13 so that theend of tabs 11a are flush with the end face of wall 7c and both abutagainst wall 1b.

In this case the bare fiber 35 is forced into the position relative tocapillary ferrule 25 at which it was in during the cleaving operation asis shown in FIG. 5a. The end of bare fiber 25 will thus be flush withthe free end of the capillary ferrule 25. In this regard, it is possibleto not cleave the bare fiber 25 until the entire connector is assembledsince when the connector is assembled, the ends of tabs 11a and the faceof wall 7c will be flush as in the case of the previously discussedcleaving operation. Cleaving can then be performed.

When it is desired to connect the connector of the invention to a likeconnector, the adaptor body 40 is provided which is made up of two likepieces 41 held together at screw holes 49 by respective screws, as shownin FIG. 3, passed therethrough. When assembled, the pieces 41 define apassageway 51 therethrough with a centering sleeve 53 serving to alignthe pieces 41 when being assembled. Once assembled, ridges 45 serve toprevent the centering sleeve 53 from sliding out of the adaptor.

A ferrule centering sleeve 47 is also received inside the sleeve 53 andserves to frictionally receive ferrule 25 for centering and aligning itwith a like ferrule 25 of another connector. Thus, to assemble twoconnectors together, the adaptor 40 is threaded to the coupling nut 5 atthreads 43 and the capillary ferrule 25 received in sleeve 47. A likeconnection is effected on the other side of the adaptor 40. Further, inorder to ensure repeatability of results, the adaptor 40 includes, aspreviously discussed, slots 55 which engage with key tabs 6 of frontbody 1 to ensure repeatable relative rotational positioning of oneconnector body with respect to another.

Inside the rear body 3, the capillary retainer 7 is dimensioned toprovide a predetermined clearance with the inner wall of the front body1 thereby providing a free-floating structure in a direction transverseto the longitudinal axis of the connector. The clearance between theother elements and the inner wall of front body 1 or rear body 3 mustthen be such as to not impede said free-floating structure. Thus, forexample, the clearance between compensator body 9 and the inner walls ofrear body 3 must be at least as great as that between the inner wall offront body 1 and capillary retainer 7. A like clearance is also providedbetween sleeve 47 and sleeve 53 in the adaptor 40.

With respect to the sleeve 47, this sleeve can be a triangular splitsleeve as shown in FIG. 6, or a cylindrical sleeve as in FIG. 7. Thesleeve will preferably be of smaller cross-section than the ferrule 25and due to spring tension will compressively hold the ferrule 25. Theonly requirement is that it be constructed such that if the ferrule 25is inserted not in alignment with the longitudinal axis thereof, it besufficiently resistant to bending to force the ferrule 25 back intoalignment in cooperation with the above-discussed free-floatingstructure. Thus, due to the spring loaded compensating mechanism, as canbe appreciated from the drawing, when being connected to a likeconnector, the capillary ferrule 25 will be forced inward compressing,through the described mechanism, the spring 19. Spring 13 will tend toforce the clamp body 11 against wall 1b. However, since the end of barefiber 35 will abut physically against a like end, it will not bepermitted to extend beyond the end of capillary ferrule 25. Moreover, inthe case when precise longitudinal alignment is not achieved, thecompensating mechanism will urge the respective fiber 35 out from theirrespective ferrules 25 so that they will physically contact each otherat the respective ends thereof even if the ferrules 25 only contact eachother at a partial angle and not flush with each other. Accordingly, inthese cases the spring 13 will also compress and the ends of tabs 11awill not abut wall 1b. In this regard, the spring 13 is capable ofexerting a force of only about 50-100 gms, preferably about 60 gms, toprevent damage to the faces of bare fibers 35. The spring 19 on theother hand is capable of exerting about 2 lbs of force to ensure tightconnection between the ends of the capillary ferrules 25 by cooperationwith the centering sleeve.

In an alternative construction as shown in FIGS. 8 and 9, the keymechanism can be a sleeve 8 which fits over the capillary retainer andclamp arrangement previously described. The sleeve 8 would include tabs11a" which engage slot 50 of the capillary retainer 7, which is thiscase would extend out from the body of retainer 7 or be of otherequivalent construction as will be apparent to those of ordinary chillin this art. To prevent rotation, the sleeve 8 would be forced againstthe front wall 2b of, in this case a one-piece body 2, by a modifiedcable clamping mechanism. More particularly, while not showing the innersleeve 21, it would be inserted in the cable 27 as discussed previously.A sleeve 37 would be received over the cable 27 and crimped thereon withturned out portion 37a abutting against sleeve 8 in body 2. An outerholder 10 would then be threaded by engagement between threads 2a and10a by turning at portion 10b to secure the cable 27 to the body 2. Inthis case, the sleeve 8 would house the spring 19 within it. The sleeve8 would then abut at 11a" at walls 2b.

In a still further modification for use with multimode fiber opticcables, the compensating mechanism can be omitted since gap creationbecomes less important. In this case a fiber holding mechanism as inFIG. 9 can be employed. The capillary retainer 7" holds the capillaryferrule 25. A clamp 17" is engaged at threads 17a" to the capillaryretainer 7". The buffered fiber 33 is held by deformable material 17b"such as lead by crimping of clamp 17". The key mechanism and cablesecuring mechanism will be as discussed with reference to FIG. 8 andmore clearly shown in FIG. 9.

The materials employed in practicing the invention are well known andconventional as will be readily apparent to those of ordinary skill inthe art. Thus, they will not be discussed in further detail herein.Except as otherwise noted, all parts are preferably of metalconstruction. More particularly, the fiber clamp of the preferredembodiment will be plastic with the capillary ferrule preferably ofceramic.

While particular embodiments of the present invention have been shownand described, it will be obvious to those skilled in the art thatvarious changes and modifications may be made without departing from thescope of the invention and its aspects. Accordingly, the aim of theappended claims is to cover all such changes and modifications as mayfall within the true spirit and scope of the invention.

What is claimed is:
 1. A fiber optic cable connector, comprising:a bodyhaving two ends; cable connection means for connecting a fiber opticcable of the type having a fiber extending through the center thereofwith the fiber concentrically surrounded by a buffer layer to said bodyat one end thereof in a manner such that a portion of the cable havingthe fiber surrounded by the buffer layer and a portion of the cablehaving the fiber stripped of its buffer layer extends into said body;fiber retention means for holding the buffer layer covered fiber at aterminated portion of the buffer layer wherefrom the fiber extends, andfor holding the bare fiber extending from the terminated buffer layer infixed relationship with respect to said fiber retention means, andwithin said body capillary ferrule means for receiving said portion ofsaid bare fiber therein in a manner such that said fiber is slidablewithin said capillary ferrule means and further including capillaryretaining means for holding said capillary ferrule means in fixedrelationship with respect thereto and in a manner extending frm the oherend of said body, and such that said capillary retaining means isretained within said body; spring means for urging said capillaryretaining means toward said other end of said body and for permittingsaid capillary ferrule means to retract into said body upon a forcebeing applied thereto when said connector is connected to a likeconnector; and compensating means for permitting termination of saidfiber in a manner such that it is urged outwardly from the end of saidcapillary ferrule means when said connector is assembled, and when saidconnector is connected to a like connector for maintaining the end ofthe fiber flush with the end of said capillary ferrule means, wherebyphysical contact between the ends of two bare fibers is obtained byconnecting said connector to another like connector and maintained undervarying temperature and alignment conditions.
 2. A connector as in claim1 wherein said body has internal walls defining a cavity therein, andsaid capillary retaining means is spaced from the internal walls of saidbody by a predetermined distance to provide a free-floating structure ina direction transverse to the longitudinal axis of said body.
 3. Aconnector as in claim 2 further comprising, in combination, adaptormeans for being connected to respective ends of like connectors, saidadaptor means further comprising centering sleeve means for aligningrespective capillary ferrule means of respective connectors forconnection together.
 4. A connector as in claim 3 wherein said centeringsleeve means is spaced from inner walls of said adaptor means by anamount equal to the spacing between the internal walls of said body andsaid capillary retaining means to maintain said free floating structure.5. A connector as in claim 4 wherein said adaptor means furthercomprises non-rotating key means for ensuring connection of respectiveconnectors in predetermined positions with respect thereto.
 6. Aconnector as in claim 3 wherein said adaptor means further comprisesnon-rotating key means for ensuring connection of respective connectorsin predetermined positions with respect thereto.
 7. A connector as inclaim 1 wherein said cable connection means comprises crimp means at oneend of said body for being crimped onto the outside of said cable, saidcable having arranged concentrically in sequence from the buffer layerto the exterior, a strength layer and a cover, and inner sleeve meansfor being received inside said cable around the buffer layer and barefiber thereof with the strength layer and cover thereof crimped betweensaid inner sleeve means and said crimp means.
 8. A connector as in claim7 wherein said inner sleeve means is crimpable for holding said cable atthe buffer layer thereof.
 9. A connector as in claim 1 wherein saidcompensating means comprises a spring positioned in manner such as toexert a predetermined force along the longitudinal axis of said barefiber for urging said bare fiber within said capillary ferrule means ina direction toward connection with a like connector sufficient to causesaid bare fiber to physically abut against a like bare fiber of anotherconnector but insufficient to cause damage to the end of said barefiber.
 10. A connector as in claim 9 wherein said compensating meansspring is constructed for exerting substantially less force on said barefiber than said spring exerts on said capillary ferrule means.
 11. Aconnector as in claim 1 further comprising non-rotating key means forpreventing rotation of said bare fiber about its longitudinal axisrelative to said body.
 12. A connector as in claim 11 further comprisingin combination adaptor means for being connected to respective ends oflike connectors, said adaptor means further comprising centering sleevemeans for aligning respective capillary ferrule means of respectiveconnectors for connection together.
 13. A connector as in claim 12wherein said non-rotating key means is a bent out tab integral with saidbody.
 14. A connector as in claim 1 further comprising in combination,adaptor means for connecting respective ends of like connectorstogether, said adaptor means further comprising centering sleeve meansfor aligning respective capillary ferrule means of respective connectorsfor connection together.
 15. A connector as in claim 14 wherein saidcentering sleeve means is a metal split sleeve of circular cross-sectionand substantially rigid to resist any forces transverse to the connectorlongitudinal axis exerted by said spring.
 16. A connector as in claim 14wherein said centering sleeve means is a metal split sleeve oftriangular cross-section and substantially rigid to resist any forcestransverse to the connector longitudinal axis exerted by said spring.17. A connector as in claim 14 wherein said adaptor means furthercomprises non-rotating key means for ensuring connection of respectiveconnectors in predetermined positions with respect thereto.